Space and time go hand in hand, right?
Well, “time is relative” as Albert Einstein once said. Just look at Einstein’s Theory of Relativity in which space and time are joined and create the fabric of the entire universe, otherwise known as “space-time.”
Time is not as straightforward as you may think. Space-time is not flat. Instead, it is curved. In life, we experience time. However, in Physics “experience is represented by the distance traveled, and this entire thing is called the Relativity of Time.”
Therefore, space-time can be warped by energy and matter.
This warp in time can appear to change time. Depending on where you are positioned and the speed at which you are traveling, time can appear to go faster or slower, relative to those in different parts of space-time.
So, “does this affect astronauts?” we hear you ask. Well, yes. Astronauts on the International Space Station age a little bit slower than us on Earth, but only by a minuscule amount. This is due to time-dilation effects where time appears to move slower when close to colossal objects because of their gravitational force that bends space-time.
You may be thinking this is something out of a sci-fi movie and while the concept of time dilation has been used many times in blockbusters such as Interstellar, the reality may not be as extreme.
The International Space Station orbits the Earth at an immense speed of 17,500mph. Nasa instructor Robert Frost states that astronauts experience a time dilation of around -0.00002646 seconds every day.
Therefore, if an astronaut stayed on the ISS for 180 days or so, the total time dilation would amount to -0.0047628 seconds. If a crew member wanted to become a second younger in orbit, they would have to stay on the ISS for nearly 140 years.
While time is altered, the aging process stays the same. This is because aging is not relevant to the relative time. Cells in the body age at the same rate no matter the time dilation that is experienced.
Living in space is no easy feat. The heightened radiation can prematurely age a person and the stresses of orbiting life can actually make humans age faster. If an astronaut was to experience large time dilation, they would have to travel to close the speed of light.
You can see a more detailed experiment on aging in space from NASA via the link here.
Time can move slower the faster you move as well. This is called “relative velocity time dilation.” Though no experiments have been done, for obvious reasons, one theory is that of the twin scenario.
One twin is sent into space on a rocket that travels close to the speed of light while the other twin stays on Earth. When the twin from space returns to earth, they have only aged a few years while their Earth dwelling twin has aged over a decade. Evidence seems to back this up.
Scientists sent an atomic clock into orbit and back while they kept an identical clock on Earth. The orbiting clock returned with a time slightly behind the Earth version.
The closest thing to time travel? We’d say so!
Is time the same in space?
Space and time are the same; space-time. You have probably heard this many times and, to this day, time is a very complex subject for physicists.
Albert Einstein showed us that time and space are linked while the progression of time is relative and not absolute. It is generally agreed that time is the property of the universe and science is based on the laws of physics and its assumptions.
Time on Earth is different from that in space. This is because of “relativistic time dilation.” Relativity tells us that time is the fourth dimension of space-time. As Einstein showed with his famous equation E=MC2, mass and energy are the same.
He also showed us that mass and energy help to cause space-time to curve. The true effect of this curvature is gravity.
Velocity and mass cause time to slow. If you are in a strong gravitational field, you will experience a normal passing of time. An observer from outside this field will see time passing more slowly.
The orbital speed of an object causes time to slow. Gravity is reduced when in orbit compared to being on a surface and this can cause time to speed up. While orbiting Earth, these can cancel out an altitude of half the radius of the planet.
This is why astronauts on the ISS age slightly slower than those on Earth. The velocity component of time dilation is far greater than the reduced gravity effect.
A clock on a GPS satellite that is in high orbit will run faster than if it was on Earth’s surface. This is because of the reduction in gravity that has a more substantial effect than orbital speed. The clocks on these satellites have to have their clocks slowed down regularly to match the surface time of the Earth.
Time moves slower as gravity increases. This is known as “gravitational time dilation.” This means time passes slower for objects that are closer to the Earth’s center where the gravity is much stronger.
However, this does not mean that living in an underground cave to get closer to the center of the Earth will slow down time as the effect on time is not noticeable on such a small scale.
Interestingly though, if you spend your entire life in an underground dwelling, you could age a fraction of a second slower than everyone who lives above ground.
Overall, time is variable and changes in the proximity of mass. A person near a black hole would experience a much slower rate of time. With less extreme gravity on Earth, a person here may grow into old age while the person near the black hole would hardly age at all.
It is hard to conceive but this is exactly what the theory of relativity predicts. At the singularity of a black hole, time stops and can cease to exist. Also, at the speed of light, time stops so light traveling across the universe could take no time to travel an infinite distance.
It’s time for a lie-down!