Bitcoin is the clock

By Gigi

Translation & Proofreading/Min Min & A Jian

A clock with a bright glow hangs high in the sky.

There is no right or wrong time to announce it.

—Robert Frost, My Familiarity with the Night (1928)

We still haven't figured out the great mystery of time. Time is just a concept; we don't even know if it really exists...

—Clifford D. Simak, Shakespeare’s Planet (1976)

As the saying goes, time is money. And conversely, money is also time: time is all the economic energy stored in the human body. However, the relationship between time and money is much more complicated than it seems at first glance. If it takes time to create money, money will not be money, at least not for long. Thinking deeper, tracking things in the information world is tracking time.

When money is digitized, we have to agree on a definition of time, and that’s the problem. Maybe you think telling time is as simple as glancing at the clock next to you. If you’re just doing your daily work, you can think so. But when you want to synchronize the progress of a global, distributed network of people doing their own things, telling time becomes a huge problem. If the clock can’t be trusted, how do you get the right time? If your system spans galaxies, how do you establish the concept of time? In a world without clocks, how do you measure time? What is time?

To answer these questions, we must further understand the concept of time and how Bitcoin created its own unit of time (block time, which is what we usually call block height). The questions we will explore include: Why is timekeeping ultimately linked to bookkeeping? Why is there no absolute time in a decentralized system? How does Bitcoin use causality and unpredictability to define the tense of "now"?

Timepieces have revolutionized civilization many times. As Lewis Mumford said in 1934, “The most important machine of the industrial age is not the steam engine, but the clock.” Today, timepieces are revolutionizing modern civilization once again: the most important machine of the information age is not the computer, but the clock. And that clock is Bitcoin.

track

"Children learn to count things so that they can acquire the concept of number. When counting, these things can be treated as if they are all the same, they can be single objects or groups of objects."

—David Eugene Smith, The Teaching of Elementary Mathematics (1900)

In general, there are two ways to keep track of things: physical tokens and ledgers. You can either use physical objects in the real world, such as shells, coins, or other tangible things (to express the corresponding amount), or you can replicate the state of the world by recording what has happened on a piece of paper.

Imagine you are a shepherd who wants to make sure every sheep returns home. You could put a collar on each sheep, and every time a sheep returns home, you take off the collar and hang it in the shed. Assuming each collar is hung on a separate hook, as long as the hook is full, it means that all the sheep have returned home. Of course, you can also count them each time and make a list. However, before you start counting, you have to make a new list to prevent double counting or missing counts.

Money is essentially a tool for tracking debts. In general, the things that have served as money so far can be divided into two categories: physical artifacts and lists of information. More commonly, they are tokens and ledgers.

It is important to understand the essential difference between these two types of money. Let me be clear here: physical tokens directly represent the state of things; ledgers indirectly reflect the state of things. Each has its own advantages and disadvantages. For example, tokens are physical and distributed, while ledgers are information-based and centralized; tokens are inherently trustless, while ledgers are not.

In the digital world, we can only use ledgers (although there are always many "gurus" who want you to believe that there are other ways). This is the information world, not the material world. Even if you define a certain type of information as a "symbol", it is still a piece of plastic information written to a hard drive or some information storage medium, presented in the form of an information record.

All digital information is essentially a ledger, which is the root cause of the "one coin, multiple spends" problem. Information never directly represents the state of the world. In addition, the movement of information also means that the information can be copied. Information exists somewhere. To "move" information, you must copy it to another place and then delete the original information. This problem does not exist in the physical world. Moving is moving, and it does not mean copying. The information world does not have this characteristic. If you want to "move" information from table A to table B, you must copy the information from table A to table B. There is no other way.

Another way of thinking is "uniqueness". Physical tokens are unique combinations of atoms that cannot be easily copied. Pure information does not have this property. If you can read a message, you can perfectly copy it. Therefore, we can conclude that physical tokens have uniqueness, while digital tokens do not. I even think the term "digital token" is questionable. Tokens can represent secret information, but they can never represent unique, uncopyable information.

This difference in characteristics suggests that information cannot actually be “transferred.” Digital tokens cannot be transferred the way physical tokens can, because you cannot be sure that the original owner has destroyed the information. Like all information, digital tokens can only be spread like ideas.

“…if you have an apple and I have an apple, we can swap apples and each of us still has one apple. But if you have an idea and I have an idea, we can swap ideas and each of us will have two ideas.”

——Charles F. Brannan (1949)

Physical tokens (what we call physical bearer assets, or “cash”) do not face this dilemma. In the physical world, if you give me a coin, you lose it. There is no magic way to duplicate it, and in order for me to have a coin, I must have been given a coin. The laws of the physical world prevent you from spending more than one coin.

While multiple spending does happen in the non-digital world (notorious con man George Parker once made a profit by selling the same property multiple times, including landmarks like the Brooklyn Bridge), it requires an elaborate scam and gullible buyers. The digital world is different.

In the digital world, since we are always dealing with information, multiple costs are an inherent problem. Anyone who has copied a file or used the copy-paste function knows that information can be perfectly reproduced and is not tied to the medium in which it is stored. Suppose you have a digital photo, you can copy it a million times, save some of the copies to USB sticks, and send them to thousands of people. Perfect copies are achievable because perfect corrections can be used to eliminate all imperfections. Most importantly, the cost of copying is almost zero, and the copies are indistinguishable from the original.

Let me say it again: information can only be copied. Digital information cannot be moved from A to B, it can only be copied from A to B. If the copy is successful, and the original at A is deleted, it can be called a "move". This is why the multi-spending problem is so tricky. Without an authority, there is no way to transfer any information from A to B without counterparty risk. We have to trust that the original will be deleted. A natural side effect is that with digital information, we cannot be sure how many copies there are and where they are.

Therefore, digital tokens can never be used as money. Tokens have reliability because of their unique physical structure and are difficult to copy. In the digital world, this advantage is gone. In the digital world, tokens are unreliable. Due to the inherent characteristics of information, the only viable form of digital currency can only be a ledger, not a token. Therefore, digital currency has to face the problem of time.

Symbols do not have time attributes, and ledgers are not

“What is seen is temporary, what is unseen is eternal.”

—Paul of Tarsus, Corinthians 4:18b

For physical tokens, it doesn’t matter when the transaction takes place (where your money comes from). You either have money in your pocket or you don’t. You spend it or you don’t. The only prerequisite for spending money is that you have money in your pocket. The rest is left to the laws of nature. In this sense, physical tokens are trustless and timeless.

Physical possession is less important for a ledger. The people who manage the ledger need to make sure that all entries are in order. Characteristics that were originally imposed by the laws of physics (you can't spend money that doesn't belong to you, and you can't spend the same money twice) must be enforced by human-made rules. It is these rules (not the laws of physics) that keep the ledger in order.

The problem is the shift from physical laws to human-made rules. The latter can be modified and broken, but the former cannot. For example, you can’t “forge” a physical gold coin; you have to dig it out of the ground. But you can forge gold coins on paper. You just add an entry to a ledger saying you have some gold coins. In the case of a central bank, it only takes a few keystrokes on a computer to create trillions of dollars. (Financial professionals call this “rehypothecation,” “fractional reserve banking,” and “quantitative easing” — but don’t be confused by the fancy terms; they’re all fake money.)

To ensure that the ledger and the people who manage it are not falsifying information, we must have independent audits of the ledger on a regular basis. It is not a big deal to reconcile every entry in the ledger. Auditors need to be able to check past ledgers to ensure the reliability and validity of the ledger. Without reliable timestamps, we cannot verify the internal consistency of the ledger. We must have a mechanism to determine the order of transactions.

Without an absolute concept of time, we cannot determine the order of transactions. If we cannot determine the order of transactions, we cannot ensure that the ledger is not forged. In addition, how can we verify how much money you have? How can we ensure that all accounts are in order?

The distinction between tokens and ledgers highlights the need to track time. In the physical world, money is an artifact without a time attribute that can be used for transactions without human supervision. In the digital world, marking money requires a timestamp.

Centralized currency tokens

“Time can leave marks on everything, but it can also erase them.”

——Yahia Lababidi (b. 1973)

The most common way to solve the multi-spend problem (ensuring that each digital transfer only happens once) is to create a centralized list of transactions. Once you have a centralized list of transactions, you have a ledger that can act as a single source of truth. At this point, solving the multi-spend problem is as simple as double-checking the list of transactions to make sure that every entry is correct. This is how PayPal, Venmo, Alipay, and all banks around the world (including central banks) solve the multi-spend problem: with an authority.

“The problem with this process is that it is difficult for the recipient to verify whether a previous holder has spent a sum of money multiple times. The usual solution is to introduce a trusted third-party authority, or an institution like a mint, to verify each transaction to prevent multiple payments… The problem with this solution is that the fate of the entire monetary system is completely dependent on the operator of the mint, because every transaction must be confirmed by the mint, which is like a bank.”

—— Satoshi Nakamoto, White Paper

It is important to note that Satoshi Nakamoto could not make information uncopyable. Every part of Bitcoin (source code, ledger, user's private key) is copyable. All of this can be copied and tampered with. However, Satoshi Nakamoto successfully created a system that makes copies that break the rules useless. The Bitcoin network implements a complex mechanism to determine which copies are useful and which are not. It is this mechanism that brings scarcity to the digital world. This mechanism is like a dance that needs to be controlled.

Even centralized ledgers must use a unified time tracking method to solve the problem of multiple payments. When a transaction occurs, we must know the transaction party, the transaction amount, and most importantly, the transaction time. In the information field, there is no way to mark currency without a timestamp.

“It is important to emphasize that decentralized ledgers were not possible until Satoshi Nakamoto invented a solution because we had not been able to solve the problem of associating events with time points in distributed systems.”

——Gregory Trubetskoy (2018)

Decentralized clock

"Time will take away everything."

—Aeschylus (525-456 BC)

Time and order are closely related. As Leslie Lamport wrote in his 1978 paper, "Time, Clocks, and the Order of Events in a Distributed System," "The concept of time is fundamental to the way we think. It is derived from a more fundamental concept, namely, the order in which events occur." Without a central coordinating point in time, seemingly intuitive concepts such as "before," "after," and "simultaneously" lose their reference. In Lamport's words, "The concept of 'what happens first' defines the order of events that does not change in a distributed multiprocess system."

In other words: if we can't have someone in charge of keeping time, then how can we be sure of the order in which events occur? How can we have a reliable clock without a central reference system?

You might think this problem is easy to solve, since everyone can just use their own clock. But this only works if everyone's clock is accurate (and everyone follows the rules). In a system where people have opposing, conflicting interests, everyone using their own clock would be a disaster. And, according to relativity, this approach doesn't work across space.

Here’s a thought experiment: if you lived in a world where everyone kept track of the order in which events occurred, how could you deceive others? You could pretend that a transaction you sent today was actually from yesterday (it was just delayed for some reason), so that the money you spent today would still be yours. Since every decentralized system inherently communicates asynchronously, the above scenario is not just a theoretical thought experiment. Messages do get delayed, and timestamps can be inaccurate. Add in relativistic effects and the natural speed limit of the universe, and it’s hard to discern the order of events without a centralized authority or observer.

“Who's there? Knock knock.”

—— Classic pun

To better illustrate this, let's look at a concrete example. Imagine that you and your business partner both have access to your company's bank account. Your business is global, so your bank account is in Switzerland, you live in New York, and your business partner lives in Sydney. It is January 3rd on your end, and you are enjoying a weekend night at your hotel. Your business partner's end is Monday morning, and she decides to buy breakfast using the debit card in her shared bank account. The balance on the card is $615. It is 8:21am local time. Her breakfast costs $27.

At the same time, you plan to pay for your room with another debit card linked to the bank account. The balance on the card is $615. It is 5:21 PM local time. The room costs $599.

That is, you swiped your card at the same moment. What would happen? (Physicists, forgive me for using the expression “at the same moment”; we are ignoring the effects of relativity and the fact that there is no absolute time in the universe. We are also assuming that the concept of synchronous events exists. Bitcoin is complicated enough!)

The bank’s central ledger is likely to receive both transactions one after the other, so one of you must be lucky and the other unlucky. If the central ledger happens to receive both transactions at the same instant (accurate to the millisecond), the bank must decide who gets to spend the money.

So what happens if there are no banks? Who decides which transactions are made first? What happens if it’s not just the two of you, but hundreds or even thousands of people trading at the same time? What if you don’t trust these people? What if someone wants to do something malicious, like set their own clock back and pretend that their transaction was made a few minutes ago?

“We need a time-dependent tool to create a recognized ordering and maintain a unique history without relying on any central coordinator.”

—Giacomo Zucco, Discovering Bitcoin (2019)

This is why all previous attempts at digital cash have relied on a centralized registry. That is, we have to trust someone to correctly determine the order of transactions. We need a centralized party to act as a centralized clock.

Bitcoin solves this problem by redefining time. Bitcoin measures time in blocks rather than seconds.

Blocks are used as time units

The emperors settled their disputes, which was the grace of the time;

Expose the lies and let the truth come to light;

Seal the past with the marks of time;

Hold fast the night and wake up the dawn;

Punish the wicked until they repent;

— William Shakespeare, The Rape of Lucrece (1709)

All clocks rely on a regular process, which we often call a "tick-tock". In essence, the ticking sound of a grandfather clock is no different from the hum of modern quartz and atomic clocks. Specifically, we measure seconds or minutes by the number of times a part in the clock oscillates or vibrates.

Large pendulum clocks have long, noticeable pendulums. Smaller, more specialized clocks require special components. How often a clock vibrates (how often it "ticks") depends on its application.

Most clocks vibrate at a fixed frequency so that they can tell time accurately. However, some clocks vibrate at a variable frequency. For example, a metronome can be set to a certain frequency, and once set, it will beat at a constant frequency. The time interval between each Bitcoin "tick" is different because of the probabilistic mechanism inside. However, the purpose of both is the same: to play music so that the dance can continue.

Isn’t Bitcoin a clock? Satoshi Nakamoto did hint that the entire Bitcoin network is like a clock, or in his words, a distributed timestamp server.

In this paper, we propose a solution to the multi-spending problem by generating computational proofs of the order in which a set of transactions occurred using a peer-to-peer distributed timestamp server.

— Satoshi Nakamoto, Bitcoin: A Peer-to-Peer Electronic Cash System (2009)

From the references at the end of the Bitcoin white paper, it is clear that timestamps are a fundamental issue. Among the 8 references, 3 are related to timestamps:

• How to Timestamp Digital Documents, S. Haber, WS Stornetta (1991)
• "On How to Improve the Efficiency and Reliability of Digital Timestamping", D. Bayer, S. Haber, WS Stornetta (1992)
• How to Design a Trust-Minimized Secure Timestamping Service, H. Massias, X.S. Avila, J.-J. Quisquater (1999)

Time is a chain of cause and effect

To take it more extreme, the whole world is nothing more than a network of relationships.

—Tim Berners-Lee, Weaving the World Wide Web (1999)

Falsifying dates is a universal problem, not just in the digital world. In a kidnapping, for example, the kidnapper needs a way to prove when the kidnapping took place.

- Time proves -

This method is feasible because newspapers are difficult to forge and easy to verify. Since the front page of a newspaper reports events from the previous day, it is impossible for the kidnappers to know the front page news in advance and forge the hostage photos weeks in advance. Therefore, the publication date of the newspaper held by the hostage in the photo is proof that the hostage is alive.

This method highlights an important concept: causality. The arrow of time reflects the causal relationship of events. Without causality, there is no time. In the cyber world, hash functions are crucial to solving the timestamp problem because they introduce causality. Without a certain document, we cannot generate the corresponding cryptographic hash value, so there is a causal relationship between the document and the hash value: first there must be data, and then the hash value (corresponding to the data) can be generated. In other words, without the computational irreversibility of one-way functions, there will be no causality in the cyber world.

With causality, we can create a chain of events that are linked together. Therefore, secure digital timestamping schemes can write history for the digital world where time does not exist.

Causation determines the temporal order of events. If an event is caused by some previous events, which in turn cause some later events, then the event's position in history is fixed and cannot be changed.

——Bayer, Haber, Stornetta (1992)

It is undeniable that causality is crucial to economic calculation. Since the ledger is actually the embodiment of economic calculations between multiple partners, causality is also crucial to each ledger.

We need a system that allows all participants to reach consensus on a single historical record... The solution we propose is based on a timestamp server.

—— Satoshi Nakamoto (2009)

Interestingly, all the components that make Bitcoin work already exist. As early as 1991, Haber and Stornetta introduced two solutions that "can effectively prevent timestamp fraud." One is a solution that relies on a trusted third party, and the other is a more complex "distributed trust" solution that does not rely on a trusted third party. The two authors even discovered the inherent problems behind trusting the causal chain of events and the conditions required to rewrite history. In other words, "the only way to successfully do evil is to prepare a long enough timestamp chain, so long that even the most suspicious challenger cannot doubt it." Today, Bitcoin also has a similar attack vector, namely the 51% attack (see the next section for details).

A year later, Bayer, Haber, and Stornetta proposed using a "Merkle tree" instead of a simple linked list to connect all events based on previous research. The Merkle tree is a simple and efficient data structure that can calculate a certain hash value based on multiple hash values. From a timestamp perspective, this means that multiple events can be accommodated in one unit of time. In addition, the three authors also proposed an improvement on the distributed trust model they proposed in 1991, that is, to hold a "World Championship Tournament" to determine the only "winner", and the winner will publish the calculated hash value in a public place (such as a newspaper). Does it sound familiar?

We can see that newspapers are an excellent example for helping us think better about the second characteristic of time: unpredictability.

Causation and unpredictability

Time is not a reality (hupostasis) but a concept (noêma) or a unit of measurement (metron)…

—Antyphon the Wise, On Truth (3rd century AD)

Causation is important, but it is not enough. The passage of time is also unpredictable. In the physical world, we describe the passage of time by observing natural processes. We observe that entropy is increasing, and we call it the arrow of time. Although in most cases, the laws of nature seem to have nothing to do with the arrow of time, some things are actually irreversible. As the saying goes, a broken mirror cannot be mended.

Similarly, the digital world also needs entropy-increasing functions to create the arrow of time. SHA256 hashes and cryptographic signatures are not absolutely unbreakable, but just as a broken mirror is almost impossible to put back together, SHA256 and cryptographic signatures are also almost unbreakable.

Without entropy, we can change the timestamp arbitrarily. For example, the sequence of Fibonacci numbers has causal relationships, but does not have the property of increasing entropy. In the Fibonacci sequence, each number is the sum of the previous two numbers. Therefore, the Fibonacci sequence is a chain of cause and effect. However, the Fibonacci sequence cannot be used to tell time because it is completely predictable. This is like saying that a kidnapper cannot use a photo of a hostage with a calendar to prove that the hostage is still alive. We cannot use predictable things as proof of time, only things that cannot be predicted in advance, such as the front page of that day's newspaper.

Bitcoin's unpredictability is achieved through transactions and proof of work. Just like no one can predict what will be published in tomorrow's newspaper, no one can predict what the next Bitcoin block will look like. You can't predict which transactions will be included in the block because you can't predict which transactions will be broadcast in the future. More importantly, you can't predict who will solve the current proof of work puzzle and what the solution will be.

Unlike newspapers, proof of work is directly linked to events that have already occurred. Proof of work is not just a record of events, but the events themselves. It is this direct link based on probability that eliminates the need for trust in proof of work. The only way to find a valid proof of work is to make a large number of guesses, each of which takes a small amount of time. The number of guesses required to find a solution is probabilistic, forming the Bitcoin time chain.

Using the causal order of the hash chain and the unpredictability of proof of work, the Bitcoin network provides a mechanism to create an undisputed history of events. Without causality, we cannot distinguish which event came first. Without unpredictability, causal order is meaningless.

Regarding the kidnappers' approach mentioned above, Bayer, Haber, and Stornetta actually gave a clear explanation as early as 1992: "If you want to determine that a document was created after a certain time, the document must record an event that has already occurred but could not be predicted in advance."

It is this combination of causality and unpredictability that allows us to define “now” artificially in a digital world that otherwise has no concept of time. As Bayer, Haber, and Stornetta pointed out in their 1991 paper: “The order in which clients will request timestamps and the hash values ​​they will submit is unpredictable. Therefore, if we include bits from the sequence of previous client requests in the signed certificate, we know that the certificate’s timestamp is later than those requests… The requirement that the certificate must include bits from previous documents also provides time granularity in the other direction, since a timestamping authority cannot pre-issue certificates unless it has requests from this moment.”

All the components are here. Satoshi’s genius was to combine them all together, thus eliminating the need for a timestamping agency.

Time proves

Although the cause is hidden, the result is known.

—Ovid, Metamorphoses (8 AD)

Let’s recap: To spend money in the digital world, we must rely on a ledger. To make the ledger trustworthy, we must have ordering of transactions. To have ordering, we must use timestamps. Therefore, if we want to create trustless money in the digital world, we must remove any entity that creates and manages timestamps, and any single entity that is responsible for keeping time.

A genius like Satoshi Nakamoto found a solution: "In order to implement a peer-to-peer distributed timestamp server, we need to use a proof-of-work system, similar to Hashcash proposed by Adam Back."

The reason we need to use a proof-of-work system is because we need something that is native to the digital world. Once you understand that the digital world is essentially informational, it becomes obvious that computation is all we have. If your world is made of data, there will be data manipulation.

Proof of Work is a peer-to-peer mechanism because it is trustless. Proof of Work is trustless because it is isolated from all external inputs (like a clock or a newspaper). It relies on only one thing: computation requires input of work. In our world, generating work requires input of energy and time.

Bridge to Time

I know I'm obsessed.

We ran across the bridge -- the burning bridge --

The flames raged behind him,

We stand on the brink of death,

Honey, it's you and me against the world.

—Kate Bush, Burning Bridge (1985)

Without proof of work, we will inevitably encounter the problem of information input mechanism, because there will always be a gap between the physical world and the information world. The marks made on the list when the shepherd counts the sheep are not real sheep, the map cannot be compared with the real territory, and the news in the newspaper is not necessarily the real event. Similarly, even if you use the real world clock to create a timestamp, it does not mean that the actual time is like that.

Frankly speaking, we cannot trust data to represent reality unless it is a reality inherent in the data itself. The genius of Bitcoin’s variable difficulty proof-of-work is that it creates its own reality, as well as space and time.

Proof of Work is able to directly connect the digital world and the physical world. Only this connection is established in a trustless manner. Everything else relies on external input.

The difficulty of Bitcoin blocks is adjusted to maintain the connection between Bitcoin time and human time. Like clockwork, the Bitcoin system readjusts the mining difficulty every 2016 blocks. The difficulty adjustment aims to keep the average block time at 10 minutes, thus establishing a stable connection between the physical world and the information world. Therefore, the Bitcoin clock needs to be readjusted according to human perception of time. Purely clock-based difficulty adjustment is not feasible because it would completely separate Bitcoin from the human world. The purpose of the difficulty adjustment is to prevent people from producing blocks too quickly (or too slowly).

As Einstein taught us, time is not absolute. There is no such thing as cosmic time. Time is relative, and simultaneity does not exist. This fact alone makes all timestamps, especially those spanning vast distances of space, inherently unreliable, even if there is no conflict between the participants. (This, incidentally, is why GPS satellite timestamps must be constantly adjusted.)

The fact that human timestamps are not precise is not important to Bitcoin. Nor is it important that there is no absolute reference frame in the first place. Timestamps only need to be precise enough that the block time calculated based on 2016 blocks is reliable enough. To ensure this, a "physical world" timestamp for a block is only accepted if it meets the following two criteria:

1. This timestamp must be greater than the median timestamp of the previous 11 blocks.
2. This timestamp must be less than the network adjusted time plus two hours. (The "network adjusted time" is the median timestamp returned by all nodes you are connected to.)

- BitCoin v0.01 ALPHA (2009) -

Probability-based time

Time endlessly produces a fork in the road, leading to countless futures.

——Borges, "The Garden of the Trail forked" (1958)

Time is an illusion. This is especially true for lunch.

—— Douglas Adams, "A Wandering Guide to the Galaxy" (1979)

The payee needs to have evidence to prove that when each transaction occurs, most nodes agree that they first receive the transaction... When there are multiple payment objects in the same transaction, only one is valid. The payee must wait for about an hour before it can believe that the transaction is valid. At that time, the network can solve all possible multi-cost competitions.

——Samoto Nakamoto (2009)

To understand more deeply, we must go back to earlier times.

——Gordon Clark, "Understanding People and Things from a Christian Perspective" (1951)

Tick ​​tick - What time is it?

Tick ​​tick tick... Stopped at c619.

Is this true? Will it be slower?

No matter whether it is accurate or not: 8 will not be wrong before 9.

This clock is not accurate and sometimes walks upside down.

There will be ghosts only on time, and centralization is not necessary!

The clock is ticking, ticking,

It's not good to do bad things, and you'll tick to the next block.

——A poem about Bitcoin and time (2020)

Summarize

Time is still one of the biggest puzzles of physics, and even raises people's doubts about the definition of physics itself.

—Jorge Cham and Daniel Whiteson, “We Know Nothing: A Guide to the Unknown Universe” (2017)

Blockchain is just a chain composed of data blocks.

—— Peter Todd

Bitcoin is time not only reflected in one aspect. The smallest unit of Bitcoin satoshi is time because it is currency; Bitcoin’s network is time because it is a decentralized clock. It is precisely because the Bitcoin clock rotates tirelessly that Bitcoin can have these magical characteristics. Otherwise, the entire Bitcoin system will fall apart. It is also because of this amazing Internet currency that can benefit everyone.

Original link https://www.swanbitcoin.com/bitcoin-is-time/