What time is it in space?
Imagine you are in a spaceship heading to Mars and a friend just woke up after a good sleep. He asks: "what time is it?" What do you say? Do you lie and say it's a dream or would you say the truth?
You say: There is no time in space. The amount of time that has passed since the Big Bang is different everywhere, depending on the speed of a moving object. If there were two hypothetical watchers since the beginning of time, moving at different speeds, they would say a different time has passed. In addition, time is also affected by gravity. The closer you are to objects of great mass, the slower the time. You are out of time, absolute time does not exist.
Of course he will tell you: I just wanna know what time it is.
Then you'll say: oh, that's a bit different. The time as we see it, is a way of measure but we can't really measure time. We use time to measure intervals between events. We also use it to define the speed, which is the distance divided by time. Also our concept of time depends entirely on the rotation of the earth on its axis, which means that time as we know it is only useful on our planet, and nowhere else in the universe.
Your friend is going to roll eyes and look for the watch he brought from home. “Well, it’s 7:30 in Turkey, time to work”, he'll say.
That’s actually how it works. If an astronaut needs to measure time in space, he just needs a chronometer. Otherwise time, as we know it, is useless for him. Even in a spaceship as neat as The Enterprise, if he needs to know when to eat, work out, sleep, wake up and many other things, he only uses a wrist watch synchronized with the planet’s time. In that scenario he could say: “we’ll meet tomorrow at 1700, according to my watch.”
As humans in this planet, we have used clocks with the same purposes our whole lives, we just keep using them for convenience no matter the place we are.
Do they use clocks in the International Space Station?
As mentioned, they do use clocks synchronized with the Earth’s time. Clocks in the ISS are cofigured with GMT, the Greenwich meridian, UK. This puts the crew 5 to 6 hours ahead of the mission control center in Houston, TX, and 3 hours behind the mission control center in Moscow. That means the flight controllers in US have to start working very early, and the ones in Russia have to work late.
Up in the ISS they don’t have day and night, because the station completes an orbits around the whole planet every 90 minutes. They get to see 15 sunrises ans sunsets every 24 hours. Adapting to this is critical, so they have a very tight schedule.
The time measured by astronauts, as well as the measured down here, is referential but we can’t live without it. We need it to complete our circadian cycles. If you were locked for two weeks in a room without any contact to exterior, you will be so disoriented that you could begin to sleep more than usual, or perhaps less. You’ll have no idea what day is it and your calculations will be useless. This has been tested several times, even by Michael Stevens (Vsauce) in his series Min Field.
Measuring time is extremely necessary and, if we want to advance in outer space exploration, we need to use something more precise than regular clocks, atomic clocks.
What’s the difference between an ordinary and an atomic clock?
The main difference is that the oscillation inside an atomic clock goes between the atom nucleus and the electrons around it. That oscillation is not exactly like wheels and springs in a mechanic clock.
The frequencies inside the atom are determined by the core’s mass and the gravity. It works like an electrostatic spring between the core’s positive charge and the electrons cloud surrounding it.
There are different types of atomic clocks but all of them follow the same basic principle. The difference is associated with the element used and the ways to detect when the energy levels change.
The first type of atomic clock uses cesium. For this type of clock a beam of cesium atoms is used.
The second uses hydrogen, this clock keeps the hydrogen atoms at the level of energy required, inside a container with walls made of a special material, so that the atoms do not lose their energy too quickly.
The next type uses rubidium. It is the simplest and most compact of all atomic clocks.
Why shall we use atomic clocks and not ordinary ones?
Most watches we use now are based on a quartz oscillator. Because the quartz crystals vibrate at a regular frequency, when a small electric current is applied, they can be used for time measuring.
That is perfectly fine for our everyday purposes but, over time, these quartz oscillators lose accuracy. After only six weeks they can be delayed up to one millisecond or one thousandth of a second. It may not seem like much, but imagine if you want to use one of these for space navigation. If you trust these clocks in a travel through space, that small fraction of a second could mean a distance error of 300 kilometers.
Atomic clocks are based on the oscillations of excited atoms. In physics this excitation is the addition of a slight amount of energy (called excitation energy) to a system. That system can be an atomic nucleus, a whole atom or a molecule. When this energy is added, it can result in the alteration of this system.
Atomic clocks keep time better than any other clock, even better than the Earth’s rotation and the stars movement. Without atomic clocks, GPS navigation would be impossible, the Internet would not be synchronized and the position of the planets would not be known with sufficient accuracy for space probes and landing devices to be launched and monitored.
They are incredibly accurate. The most precise ever made wouldn't win or lose a second in a billions years. Imagine that on space travel.
Today we have satellites with atomic clocks that use cesium and rubidium atoms and, although they are much more precise than a quartz oscillator, they still deviate. Corrections should be made twice a day from atomic clocks the size of a refrigerator, here on the ground.
Deep Space Atomic Clock
Recently NASA has launched the Deep Space Atomic Clock into orbit, which is based on electrically charged mercury atoms. This atomic clock is up to 50 times more accurate than cesium and rubidium clocks inside GPS satellites. Its accuracy only changes one second every 10 million years. It's only the size of a toaster, but it could revolutionize deep space travel. It’s as stable as atomic clocks in land. That means that instead of the bi-directional signal system, currently in use, the Deep Space Atomic Clock could be used to perform tracking calculations, right out there on the spacecraft, after receiving a signal from the earth.
That directional tracking could mean faster and more flexible navigation, with minimal entry to the ground. Which would result in faster response times to unexpected events and more precise course corrections. It can provide us with spaceships that adapt on the fly.
This also can lighten the load on the NASA Deep Space Network, which would allow it to simultaneously manage many spacecraft, while exploring the solar system without the need to expand it to other equipment. It could change the way we navigate the stars.
I say “could” because it will be tested first for a year. Hopefully everything goes well.
Sources:
What is an atomic clock and how does it work?
https://science.howstuffworks.com/question40.htm
What time zone is used on International Space Station?
https://qr.ae/TWvxY8
How Atomic Clocks Work
https://science.howstuffworks.com/atomic-clock2.htm
You say: There is no time in space. The amount of time that has passed since the Big Bang is different everywhere, depending on the speed of a moving object. If there were two hypothetical watchers since the beginning of time, moving at different speeds, they would say a different time has passed. In addition, time is also affected by gravity. The closer you are to objects of great mass, the slower the time. You are out of time, absolute time does not exist.
Of course he will tell you: I just wanna know what time it is.
Then you'll say: oh, that's a bit different. The time as we see it, is a way of measure but we can't really measure time. We use time to measure intervals between events. We also use it to define the speed, which is the distance divided by time. Also our concept of time depends entirely on the rotation of the earth on its axis, which means that time as we know it is only useful on our planet, and nowhere else in the universe.
Your friend is going to roll eyes and look for the watch he brought from home. “Well, it’s 7:30 in Turkey, time to work”, he'll say.
That’s actually how it works. If an astronaut needs to measure time in space, he just needs a chronometer. Otherwise time, as we know it, is useless for him. Even in a spaceship as neat as The Enterprise, if he needs to know when to eat, work out, sleep, wake up and many other things, he only uses a wrist watch synchronized with the planet’s time. In that scenario he could say: “we’ll meet tomorrow at 1700, according to my watch.”
As humans in this planet, we have used clocks with the same purposes our whole lives, we just keep using them for convenience no matter the place we are.
Do they use clocks in the International Space Station?
As mentioned, they do use clocks synchronized with the Earth’s time. Clocks in the ISS are cofigured with GMT, the Greenwich meridian, UK. This puts the crew 5 to 6 hours ahead of the mission control center in Houston, TX, and 3 hours behind the mission control center in Moscow. That means the flight controllers in US have to start working very early, and the ones in Russia have to work late.
Up in the ISS they don’t have day and night, because the station completes an orbits around the whole planet every 90 minutes. They get to see 15 sunrises ans sunsets every 24 hours. Adapting to this is critical, so they have a very tight schedule.
The time measured by astronauts, as well as the measured down here, is referential but we can’t live without it. We need it to complete our circadian cycles. If you were locked for two weeks in a room without any contact to exterior, you will be so disoriented that you could begin to sleep more than usual, or perhaps less. You’ll have no idea what day is it and your calculations will be useless. This has been tested several times, even by Michael Stevens (Vsauce) in his series Min Field.
Measuring time is extremely necessary and, if we want to advance in outer space exploration, we need to use something more precise than regular clocks, atomic clocks.
What’s the difference between an ordinary and an atomic clock?
The main difference is that the oscillation inside an atomic clock goes between the atom nucleus and the electrons around it. That oscillation is not exactly like wheels and springs in a mechanic clock.
The frequencies inside the atom are determined by the core’s mass and the gravity. It works like an electrostatic spring between the core’s positive charge and the electrons cloud surrounding it.
There are different types of atomic clocks but all of them follow the same basic principle. The difference is associated with the element used and the ways to detect when the energy levels change.
The first type of atomic clock uses cesium. For this type of clock a beam of cesium atoms is used.
The second uses hydrogen, this clock keeps the hydrogen atoms at the level of energy required, inside a container with walls made of a special material, so that the atoms do not lose their energy too quickly.
The next type uses rubidium. It is the simplest and most compact of all atomic clocks.
Why shall we use atomic clocks and not ordinary ones?
Most watches we use now are based on a quartz oscillator. Because the quartz crystals vibrate at a regular frequency, when a small electric current is applied, they can be used for time measuring.
That is perfectly fine for our everyday purposes but, over time, these quartz oscillators lose accuracy. After only six weeks they can be delayed up to one millisecond or one thousandth of a second. It may not seem like much, but imagine if you want to use one of these for space navigation. If you trust these clocks in a travel through space, that small fraction of a second could mean a distance error of 300 kilometers.
Atomic clocks are based on the oscillations of excited atoms. In physics this excitation is the addition of a slight amount of energy (called excitation energy) to a system. That system can be an atomic nucleus, a whole atom or a molecule. When this energy is added, it can result in the alteration of this system.
Atomic clocks keep time better than any other clock, even better than the Earth’s rotation and the stars movement. Without atomic clocks, GPS navigation would be impossible, the Internet would not be synchronized and the position of the planets would not be known with sufficient accuracy for space probes and landing devices to be launched and monitored.
They are incredibly accurate. The most precise ever made wouldn't win or lose a second in a billions years. Imagine that on space travel.
Today we have satellites with atomic clocks that use cesium and rubidium atoms and, although they are much more precise than a quartz oscillator, they still deviate. Corrections should be made twice a day from atomic clocks the size of a refrigerator, here on the ground.
Deep Space Atomic Clock
Recently NASA has launched the Deep Space Atomic Clock into orbit, which is based on electrically charged mercury atoms. This atomic clock is up to 50 times more accurate than cesium and rubidium clocks inside GPS satellites. Its accuracy only changes one second every 10 million years. It's only the size of a toaster, but it could revolutionize deep space travel. It’s as stable as atomic clocks in land. That means that instead of the bi-directional signal system, currently in use, the Deep Space Atomic Clock could be used to perform tracking calculations, right out there on the spacecraft, after receiving a signal from the earth.
That directional tracking could mean faster and more flexible navigation, with minimal entry to the ground. Which would result in faster response times to unexpected events and more precise course corrections. It can provide us with spaceships that adapt on the fly.
This also can lighten the load on the NASA Deep Space Network, which would allow it to simultaneously manage many spacecraft, while exploring the solar system without the need to expand it to other equipment. It could change the way we navigate the stars.
I say “could” because it will be tested first for a year. Hopefully everything goes well.
Sources:
What is an atomic clock and how does it work?
https://science.howstuffworks.com/question40.htm
What time zone is used on International Space Station?
https://qr.ae/TWvxY8
How Atomic Clocks Work
https://science.howstuffworks.com/atomic-clock2.htm
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