Does time exist for cosmologists?

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In summary, some cosmologists believe that time does not exist in the same way that it does for everyday humans. They believe that it can be replaced by other measures or concepts.
  • #1
Does time exist for cosmologists?

Few would deny that time - as we experience it - is a vitally important feature of life and living.

But does time exist for modern cosmology?

There are different ways of gauging time. One measure is age, say that of a horse, gauged with limited accuracy by the state of its teeth (I’ll call this a horse-measure for fun); another is the time of day, say solar time, gauged roughly with a sundial. And telling the time with quartz-oscillator watches reveals that solar time and Greenwich Mean Time (GMT) almost always don’t agree --- for reasons contributors to this forum understand. As precision of gauging increases, subtleties creep into the measuring of time, so important in our lives: relative motion affects the gauging of time, but only to a degree that hardly affects the intervals of time encountered in the everyday life of ordinary folk. The proximity of large masses similarly affects the gauging of time. Such subtleties are in physics described quantitatively with an invented language --- namely mathematics, where abstraction rules.

The judgement of which spatially separate events are simultaneous, what happened in the past, or will occur in the future, then becomes a complex matter described by General Relativity (GR). Such questions are decided by first agreeing how simultaneity is to be defined, then by considering the relative motions of observers (both as in Special Relativity), and lastly by taking into account an observers’s environment of mass/energy with GR. The importance of these factors is small in usual human experience, where simultaneity is defined by what we now see, and where one’s speed, or environment, are relatively unimportant. But accurate experiments and observations show that account must indeed be taken of them.

It has been argued (say by Julian Barbour in his bookThe End of Time) that our best abstract description of the universe, GR, does not require that time exists. In GR, as I understand it, “Now” is represented in an abstract way by hyperplanes in four-dimensional Spacetime, which itself is a sort of 'block-representation' of reality. These sections are not 'plane', but meander across Spacetime like rivers sketched on paper, along paths determined both by an observer’s motion and his/her mass/energy environment. But there are knowledgeable people (my compatriate George Ellis, for example) who believe that a description without time can’t be reconciled with our own experience. I also feel it is too Platonic.

Specifically, consider a simple and practical 'horse-measure' of age that could be used by
cosmologists who accept the current consensus: any such cosmologist --- here or elsewhere in the universe, at any epoch --- could gauge cosmic age simply be measuring (accurately) the temperature of the (almost uniform) cosmic microwave background, which is postulated to be relic radiation from an energetic and compact beginning that permeates the universe. How is the view that time does not have a fundamental existence to be
reconciled with such a simple 'horse measure'? This measure has to do with irreversible physics; ageing and the cooling of the universe, rather than GR! - latest science and technology news stories on
  • #2

yeah,I am attracted in it for a long time. In the cosmology the time could be replaced by the temperature or another measurement I forgot the name . I have had a strong feeling that it must imply some innermost meaning of the universe and the secret of the time ,which will excit us a lot.
  • #3

Maybe, just as Penrose said ,it is just the time to solve the time's secret.
  • #4

So that's why cosmologists are always late for appointments!

1. What is the concept of time in cosmology?

In cosmology, time is considered to be an essential component of the space-time continuum. It is a fundamental aspect of the physical universe and is often referred to as the "fourth dimension". Time is seen as a linear progression, in which events occur sequentially and cannot be reversed.

2. Does time exist in the same way in cosmology as it does in our everyday lives?

No, time in cosmology is not experienced in the same way as it is in our everyday lives. In cosmology, time is relative and can be affected by factors such as gravity and the speed of light. It is also believed that time may have started with the Big Bang and may not have existed before that event.

3. Can time travel be possible in cosmology?

The concept of time travel is a highly debated topic in cosmology. While some theories suggest that it may be possible through the manipulation of space-time, there is currently no evidence to support the existence of time travel. Additionally, the laws of physics as we know them may not allow for time travel to occur.

4. How does the concept of time relate to the expansion of the universe?

The expansion of the universe is closely related to the concept of time in cosmology. As the universe expands, the distance between objects increases, and time is affected as well. This is known as time dilation, where time passes at a different rate depending on the relative speed or gravitational field of an object.

5. Is time a fundamental aspect of the universe or is it a human construct?

This is a philosophical question that has no definitive answer. In cosmology, time is seen as an intrinsic aspect of the universe and is necessary for understanding the physical laws that govern it. However, some argue that time is a human construct and may not exist in the same way outside of our perception.

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