Are we at the center of the universe and whats at the edge?

  • #26
marcus
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A propos this quote by ViewsofMars about the ESA Planck mission, an earlier Planck mission webpage had this rather poetical "rabbit on the moon" description of the sensitivity with which it is mapping the Ancient Light.

Like measuring the heat of a rabbit on the Moon

The detectors will look for variations in the temperature of the CMB that are about a million times smaller than one degree – this is comparable to measuring from Earth the heat produced by a rabbit sitting on the Moon. This is why the detectors must be cooled to temperatures close to absolute zero...​
http://www.esa.int/esaCP/SEM0Y5S7NWF_index_0.html

I don't know how the ESA tech writers came up with that, or even if it is physically accurate, but I thought it was charming, and had a slight gallic flavor. It seemed somehow right for someone thinking in French to describe a quantity of heat radiation as the amount received by us from one rabbit situated on the moon.

An ant could crawl around on the earth forever and never reach an edge.
Is that how the universe as a whole works, if we went as far as we could go we would be back where we started?
That sounds right, YD, and as you later pointed out you would have to imagine stopping the expansion process in order to make it around.

But that's all right. It is OK to imagine distances with expansion stopped, so that you have time to measure or travel and they don't change while you are doing that. It helps understand the geometry.

The distance between two things that you would measure if you could stop expansion at a certain moment is called the "proper distance" at that moment. It's a technical term---in a universe with dynamically changing geometry there can be several different types or definitions of distance, this is one of the most commonly used.
 
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  • #27
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Didnt think rabbits ate cheese. Perhaps a large mouse?
 
  • #28
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Hey, thanks Marcus! :wink: (I'm writing a poem about you.:biggrin:) Adding a tad more to this subject. :biggrin: Picking up where I left off. From European Space Agency:

Planck’s new view of the cosmic theatre

11 January 2011
ESA PR-3 2011 The first scientific results from ESA’s Planck mission were released at a press briefing today in Paris. The findings focus on the coldest objects in the Universe, from within our Galaxy to the distant reaches of space.

If William Shakespeare were an astronomer living today, he might write that “All the Universe is a stage, and all the galaxies merely players.” Planck is bringing us new views of both the stage and players, revealing the drama of the evolution of our Universe.

Following the publication by ESA of the first full-sky Planck image in July last year, today sees the release of the first scientific results from the mission.

These results are being presented by the Planck Collaboration at a major scientific conference in Paris this week, based on 25 papers submitted to the journal Astronomy & Astrophysics.

Planck investigates the cosmic infrared background

The basis of many of these results is the Planck mission’s ‘Early Release Compact Source Catalogue’, the equivalent of a cast list.

Drawn from Planck’s continuing survey of the entire sky at millimetre and submillimetre wavelengths, the catalogue contains thousands of very cold, individual sources which the scientific community is now free to explore.

“This is a great moment for Planck. Until now, everything has been about collecting data and showing off their potential. Now, at last, we can begin the discoveries,” says Jan Tauber, ESA Project Scientist for Planck.

We can think of the Universe as a stage on which the great cosmic drama plays out over three acts.

Visible-light telescopes see little more than the final act: the tapestry of galaxies around us. But by making measurements at wavelengths between the infrared and radio, Planck is able to work back in time and show us the preceding two acts. The results released today contain important new information about the middle act, when the galaxies were being assembled.

Planck shows galaxy formation taking place
Planck has found evidence for an otherwise invisible population of galaxies shrouded in dust billions of years in the past, which formed stars at rates some 10–1000 times higher than we see in our own Galaxy today.

Measurements of this population had never been made at these wavelengths before. “This is a first step, we are just learning how to work with these data and extract the most information,” says Jean-Loup Puget, CNRS-Université Paris Sud, Orsay, France.

Eventually, Planck will show us the best views yet of the Universe’s first act: the formation of the first large-scale structures in the Universe, where the galaxies were later born. These structures are traced by the cosmic microwave background radiation, released just 380 000 years after the Big Bang, as the Universe was cooling.

However, in order to see it properly, contaminating emission from a whole host of foreground sources must first be removed. These include the individual objects contained in the Early Release Compact Source Catalogue, as well as various sources of diffuse emission.

Planck zeros in on anomalous emission in Rho Ophiucus
Today, an important step towards removing this contamination was also announced. The ‘anomalous microwave emission’ is a diffuse glow most strongly associated with the dense, dusty regions of our Galaxy, but its origin has been a puzzle for decades.

However, data collected across Planck’s unprecedented wide wavelength range confirm the theory that it is coming from dust grains set spinning at several tens of billion times a second by collisions with either fast-moving atoms or packets of ultraviolet light.

This new understanding helps to remove this local microwave ‘fog’ from the Planck data with greater precision, leaving the cosmic microwave background untouched.

“This is a great result made possible by the exceptional quality of the Planck data,” says Clive Dickinson, University of Manchester, UK.

Please read on . . .
http://www.esa.int/esaCP/SEMK4D3SNIG_index_0.html

What does ESA do?

ESA’s job is to draw up the European space programme and carry it through. ESA's programmes are designed to find out more about Earth, its immediate space environment, our Solar System and the Universe, as well as to develop satellite-based technologies and services, and to promote European industries. ESA also works closely with space organisations outside Europe.
http://www.esa.int/SPECIALS/About_ESA/SEMW16ARR1F_0.html
 

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