- #36
Canute
- 1,568
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But I thought the current theory is that space is expanding. Are you saying that isn't the case?
Expanding people in an expanding universe?
- Thread starter vera
- Start date
In summary, the conversation discusses the concept of expansion in the universe and whether or not objects within it, such as humans and their body parts, also expand. The general consensus is that while space itself is expanding, objects within it are not expanding as they are held together by atomic forces. The conversation also touches on the idea of a center of expansion and how it is not necessary for expansion to occur. Ultimately, the conversation concludes with a discussion on the possibility of a contracting universe and how it could affect the orbits of objects within it.
- #37
Nereid
Staff Emeritus
Science Advisor
Gold Member
- 3,401
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Echoes - sharp probes of dust
). Study of these echoes can identify all kinds of interesting things, and confirm our understand of the amount (and distribution) of dust.
Historically light has been where such echoes have been seen (e.g. from the supernova in the LMC). Recently X-ray echoes have been observed from a particularly bright GRB:
http://t2wesa.r3h.net/export/esaSC/SEMUFH474OD_sensations_0.html
There's another, independent, technique: echoes. When a really, really bright point source suddenly shows up (and then fades), it's like a strobe light through all of space between the source and us. From our point of view (POV, does anyone use this shorthand?), we will see 'circular' echoes of the flash, which are reflections of the flash off things just outside the line of sight between us and the flasher (hope that's not porn to PF
). Study of these echoes can identify all kinds of interesting things, and confirm our understand of the amount (and distribution) of dust.Historically light has been where such echoes have been seen (e.g. from the supernova in the LMC). Recently X-ray echoes have been observed from a particularly bright GRB:
http://t2wesa.r3h.net/export/esaSC/SEMUFH474OD_sensations_0.html
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