Eli5 if time is relative and gets effected by gravity how could we possibly determine the age of our universe?
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We determine the age of the universe as it relates to our frame of reference. Which is mostly what we care about anyways.
It’s an approximation. But mostly we know about how much light redshifts as it travels. We can see radiation/light from the first seconds after the big bang at the very edge of our visible universe, and can calculate how long that light has been traveling based on varies standard candles of stars in the universe which we know how far they are away from multiple independent measurements.
I would think the scientist take all that into account in their calculations. It is mind boggling to me.
Is it wrong to apply black holes to the big bang?
Like , the more mass condensed will warp spaceTime, slowing it down.
So at just after the big bang, so much mass is in so little space that time is almost zero. And as it expands and spreads , time( as in not drastically affected by mass), ramps up to one second per second as a default?
So the big bang IS the beginning of time at Zero, as we know it.
By using other constants, mainly the speed of light.
Using calculations involving light and gravity, we can calculate the distances of stuff like galaxies. The speed of light is a constant. If a galaxy is calculated to be 14 billion light years away, and we’re able to see the light it emits, that galaxy has to be at least 14 billion years old. If the galaxy is 14 billion years old, the universe has to be at least that old as well.
We aren’t sure if the universe is is fact ~14 billion years old, but we know the oldest things we’ve found are around that age.
Another theory that confirms the first is that we have measured the expansion of the universe as it is now. If we run those numbers back until the universe is miniscule (which is when the Big Bang would have occurred), we find that it would have taken roughly 14 billion years for the universe to expand to its current size.
It’s worth noting that all of these are theories, and not indisputable fact. Though there is a lot of evidence supporting the age of the universe is 14 billion years, not everyone agrees. A relatively new study from the University of Ottowa claims the universe is really ~27 billion years old.
First, time itself isnt relative.
Its the ***passage*** of time, from our frame of reference, that is relative. How we experience that passage of time does not change the abstract “age” of what we measure.
**Example**: My youngest daughter is “20 years old”. That is, she has grown and physically matured from an infant into a young adult woman.
In our normal worldly frame of reference, the process took my daughter 20 years to reach this point of her growth.
If I were to hop into a spaceship travelling close to the speed of light when she was an infant, then came back, and the trip took me 10 minutes, from my frame of reference (on the spaceship), those 20 years passed by in 10 minutes.
Just because I (*the person on the space ship*) happen to experience the passage of time for my daughter to grow up from an infant into a young adult in 10 minutes, doesnt mean she is 10 minutes old. She is still 20 years old, because from her frame of reference, it took 20 years, not 10 minutes.
So her “age” remains constant, but from 2 different frames of reference, how she and I experienced her passage from infant to young adult was different.
Its the same process for measuring the “age” of the universe. The age is constant, but we just experience the universe’s aging at a different (relative) reference frame.
If you were to hop into a spaceship going close to the speed of light, you would witness the universe’s aging process happening, but at a quicker pace. If you, on your spaceship, called me up and asked me to measure the universe’s age alongside with you, we would both end up with the same result, that being the “age” of the universe at that specific point in time.
We know the age of the universe RELATIVE to our reference point.
Something to note about the speed of light, it’s relative. You’ve heard it all the time but what does it mean?
So I’ll pose a question. A thought experiment. You’re driving a spaceship at 99.9% of the speed of light. You turn the headlights on. How fast is the light traveling? 0.01% the speed of light? 100%?
The answer is 100% of the speed of light. Because it’s relative. It’s relative to the observer (welcome quantum physics!) so in this case, relative to the spaceship.
So speed is a difficult concept to grasp in space. On earth, all of our speed is in reference to the earth itself. You’re traveling 100mph along the surface of the earth.
In space what’s the reference point? There is one. So you are a reference point for everything that you observe. Light cannot travel faster then the speed of light FROM YOUR PERSPECTIVE. According to you
So yea time is relative and the age of the universe is all weird and affected by gravity and all of it. But we can calculate the age of the universe ACCORDING TO OUR POINT OF REFERENCE.
We observe that the universe is expanding.
We observe how fast it is expanding.
With this two numbers we have one way to calculate the age.
The relativity of time has nothing to do with that.
We CANT. It’s educated guesses which we can never prove. If you’ve followed science recently, they’re now saying our universe is two times as old as they originally thought it was
Time is relative always involves frames of reference. One’s own clock always ticks normally; one might see a different clock ticking at a different rate depending on velocity and or gravity at that other clock.
We measure the age of the universe from the frame of reference of the cosmic microwave background . If we chose a different frame we would get a different value.
Actually, because mass creates gravity and mass is actually light at a very low energy state, and because we know the sun isn’t held by the gravity of the black hole in our solar system and the earth isn’t held by the sun’s gravity, and the moon etc. We invented dark matter to make it all work, then time is all screwed up. In fact, distance wise, those stars could be right next to us but the matter between us slows time so much that they look and feel very far away. Light and time are bent and slowed.
If you really want to go quantum, then according to relativity, if there is no such thing as dark matter then there is no matter between us and those distant galaxies which means there is no time between us. This means the light we are seeing is the light in real time from when it escaped the gravity field of the stars that created them. Hence when space web looked at the most distant stars they found then to be too young to even have their light reach here yet.
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