# Thread: Distance Calculations Reset

1. If I understand this article correctly, the distances of astronomical objects not bound to gravity will have to be re-calculated. If expanding space-time produces misleading range figures, then objects are actually farther away. Am I missing something?

Is expanding space a constant or variable, and do we know the metric of the expansion?

Pioneer Anomaly Solved? Interstellar Travelers of the Future May Be Helped by Physicist's Calculations

2.

3. Space is expanding but object like mars, earth and sun still stayed at the same position (why?). Planets are held at this position by gravity which resist the expansion, but what about light which is not held together by gravity?? -For light or photon: they will appear to move further and further away (faster) than expected*, this cause us to misjudge to position of the Pioneer spacecraft (since we measure the distance by reflecting photon, like a 'ping').

*light actually spreads into larger space and actually wasn't going faster than its speed limit... this spreading cause them to shift from (a more compressed) blue color to (a more sparse) red. This is called redshift.

If we detected the photon to arrive sooner, then this mean Pioneer is closer than expected, but what if Pioneer is not any closer and this photon arrived sooner because of expansion?

4. The Pioneer anomaly has a mundane explanation.

Pioneer anomaly - Wikipedia, the free encyclopedia

5. Wikipedia is not up-to-date with the theory of expanding universe (it didn't even mention it). The news just come up this month.

6. Originally Posted by msafwan
If we detected the photon to arrive sooner, then this mean Pioneer is closer than expected, but what if Pioneer is not any closer and this photon arrived sooner because of expansion?
I understand that, but this expectation is based on known flight plan and speed of the Pioneer craft. What if these variables are unknown. For example: Hubble eXtreme Deep Field.

The universe is 13.7 billion years old, and the XDF reveals galaxies that span back 13.2 billion years in time. Most of the galaxies in the XDF are seen when they were young, small, and growing, often violently as they collided and merged together....The youngest galaxy found in the XDF existed just 450 million years after the universe's birth in the big bang.
If the photons received from the Hubble eXtreme Deep Field are traveling from the largest "known" expansion of space, then isn't the image actually older than 13.2 billion years?

NASA - Hubble Goes to the eXtreme to Assemble Farthest-Ever View of the Universe

7. EDIT:
I get it. They didn't use distance to measure how old universe it. They use the color.

First: they find any stars of a know color (ie: they use the one that is called "standard candle"), and then they find how much redshift the color of the star they observe. The amount of redshift in the starlight represent how long the starlight has experienced an expansion, and thus it represent how long the star has existed in the universe. Hence, color is used to find the age of the star or galaxy.

The star might be further away than expected, but its age is still same because they measure them by color, but any star closer to us is measured using parallax angle (like how we view 3d movie); so its better than using color.

8. I understand. Thanks.

 Bookmarks
##### Bookmarks
 Posting Permissions
 You may not post new threads You may not post replies You may not post attachments You may not edit your posts   BB code is On Smilies are On [IMG] code is On [VIDEO] code is On HTML code is Off Trackbacks are Off Pingbacks are Off Refbacks are On Terms of Use Agreement