Time travel

[transam]

Is time a given no matter where on earth you are

I. E is time slightly slower or faster? At certain locations on earth??

 

[EddieM]

Is time a given no matter where on earth you are

I. E is time slightly slower or faster? At certain locations on earth??

Depends on the density of the medium it's travelling through.

 

[noseall]

Which is why gravity is able to interact with light.

Why is it?

 

[IT Minion]

Why is it?

Gravity is a result of mass and acts on mass.

 

[IT Minion]

Is time a given no matter where on earth you are

I. E is time slightly slower or faster? At certain locations on earth??

Actually it changes depending on height. The higher you get, the weaker gravity gets and the slower time passes.

Its a tiny difference but it can be measured with super accurate clocks. One at the top if a hill will fall behind one at sea level.

 

[EddieM]

Gravity is a result of mass and acts on mass.

Ok, but as pointed out photons have no mass.

 

[IT Minion]

Ok, but as pointed out photons have no mass.

But as I said, they do because they have energy. As energy is the same, in physics terms, as mass it means that gravity can act on them.

 

[EddieM]

But as I said, they do because they have energy. As energy is the same, in physics terms, as mass it means that gravity can act on them.

But they don't, they are sans mass, therefore sans energy (according to e=mc2) I not trying to be snarky, I genuinely don't understand how something without mass is affected by gravity.

 

[IT Minion]

Well we know they have energy. After all photons are just bits of light and sunlight can warm things.

Since they have energy, relativity says that's the same as saying they have mass.

 

[motorbiking]

Actually it changes depending on height. The higher you get, the weaker gravity gets and the slower time passes.

Its a tiny difference but it can be measured with super accurate clocks. One at the top if a hill will fall behind one at sea level.

Distance from the core of the mass, not necessarily height.
The weight of a kg at the top of a mountain at the North Pole may be more than the weight of a kg at closer to sea level, but nearer the equator.

 

[EFLImpudence]

Actually it changes depending on height. The higher you get, the weaker gravity gets and the slower time passes.
Its a tiny difference but it can be measured with super accurate clocks. One at the top if a hill will fall behind one at sea level.

Could it not be that in the lower gravity, just the clocks themselves actually go slower? How do they know?

For example, a day is one average rotation of the earth and hours, minutes seconds etc. divisions of that day.
It does not matter whether you live on a hill or at sea-level, nor what the clock actually says.

 

[IT Minion]

Could it not be that in the lower gravity, just the clocks themselves actually go slower? How do they know?

These days good clocks work on vibrating atoms and other things that shouldn't be affected by altitude. What you see is the atoms vibrating more slowly at height. Effectively the same as a clock ticking slower. If you take two identical clocks, take one up a tower and leave the other one at the bottom, when you bring the one up high down it will be fractionally behind.

For example, a day is one average rotation of the earth and hours, minutes seconds etc. divisions of that day.
It does not matter whether you live on a hill or at sea-level, nor what the clock actually says.

This is true, but at altitude you might have a tiny fraction of a second less In Your day.

 

[EFLImpudence]

These days good clocks work on vibrating atoms and other things that shouldn't be affected by altitude. What you see is the atoms vibrating more slowly at height. Effectively the same as a clock ticking slower. If you take two identical clocks, take one up a tower and leave the other one at the bottom, when you bring the one up high down it will be fractionally behind.

That is my point. That a clock has lost 'time' doesn't mean that time itself has altered.
If I have a clock that loses a minute a day, it is the clock that is wrong, not the day that has lengthened or gone slower.

This is true, but at altitude you might have a tiny fraction of a second less In Your day.

Again, that is my point. Are you saying that the mountain top rotates faster that the rest of the Earth?

 

[EddieM]

These days good clocks work on vibrating atoms and other things that shouldn't be affected by altitude. What you see is the atoms vibrating more slowly at height. Effectively the same as a clock ticking slower. If you take two identical clocks, take one up a tower and leave the other one at the bottom, when you bring the one up high down it will be fractionally behind.


This is true, but at altitude you might have a tiny fraction of a second less In Your day.

No, they'll be at exactly the same time altitude has no effect.

If however you synch 2 atomic clocks, then put one on an aeroplane and fly it to Australia say, then they will then be slightly out of sync.

 

[IT Minion]

Distance from the core of the mass, not necessarily height.
The weight of a kg at the top of a mountain at the North Pole may be more than the weight of a kg at closer to sea level, but nearer the equator.

When you start putting in the equator compared to the north pole it gets really complicated. You've got centrifugal force that reduces the effective gravity at the equator. When you dig into the details it's bloody complicated.