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# Why does going near a black hole have an effect on time?

I know it's to do with intense gravity in a black hole and I know motion and gravity have an effect on time. How can being near such gravity speed up everything else back in our solar system. Time is just the reoccurring actions of the earth and its orbit.

### 4 Answers

- nebLv 74 years agoFavorite Answer
Time doesn't speed up or slow down since there is no notion of absolute time in relativity. In other words, time speeding up or slowing down has to be RELATIVE to the rate of time in another reference frame and/or location. This requires that any given observer will always see time proceeding at exactly the same rate whether the observer is in or out of a gravitational field. Only when time is compared between two observers will there be a disagreement on the rate of time.

The math/physics is fairly simple. Any given observer makes measurements of time and space using their local frame of reference i.e., local clocks and rulers. By both special and general relativity (includes gravitational fields), no measurement by local rulers and clocks can distinguish the observers motion or whether they are in or out of a gravitational field. In order for this to be true for all observers, they cannot be using the same clocks and rulers. Special and general relativity specify the relationships that must exist between the clocks and rulers of different observers. In the case of special relativity, if you think of representing the clocks and rulers by coordinate axis, the coordinate axis of two observers are rotated with respect to each other so they don't make the same space and time measurements. In a gravitational field (or accelerated motion), you can think also of the coordinate axis being rotated, but rather than being fixed for a given velocity as in special relativity, the rotation changes as a function ot the relative positions of two observers. That is why space and time measurements are different for somebody in or out of a gravitational field and depend on relative positions. Since the rotation is relative, an individual observer sees no change in the way measurements are done in their particular frame.

- CliveLv 74 years ago
Because gravity, space and time are all connected and they all affect each other, as described by Einstein's theories of relativity. WHY this is, nobody knows. We just know that it is true and the equations work.

Go near a black hole and the time everywhere else is NOT speeded up. It only slows down for YOU. Time is not what you say it is - it is connected to space and is not just reoccurring actions, whatever that may mean.

- UserLv 74 years ago
It doesn't speed up everything else.

Time passes more slowly in locations of more intense gravity.

Time is NOT "just the reoccurring actions of the earth and its orbit".

That is ONE of the bases (not the only one) for some of the measures of time that we use...

but it is not time itself.

Let's take another measurement system: length.

We can use either the meter or the foot, whichever you find comfortable.

Is the foot or the meter length itself? No. Feet and meters are units used to ***measure** length. The actual length of objects varies from object to object. The foot and the meter are units used to measure those different lengths. The foot is A length, the meter is A length, but neither is length itself.

Likewise: days and years are units used to **measure** time. A day is A period of time. A year is A period of time. But neither is time itself.

For example:

You don't say of all time, "that is a year" or "that is a day". You don't say of the whole period of time that passed during last week "that was a year" or "that was a day".

- 4 years ago
Space-time is a single entity.... when one is stretched or compressed, so is the 'other.' When space is curved or warped due to gravity, time slows. The closer you are to the gravitational source, the more time slows. The stronger that source is, again, the more time slows.

It's affecting you right now - time is passing *slower* for you compared to the 6 guys on the space station. If the effect wasn't known and compensated for - your GPS unit wouldn't operate; it would 'drift' every day.