Is energy always conserved?
Physics Girl・2 minutes read
The expansion of the universe leads to redshift, where light wavelengths elongate and cool in color, challenging energy conservation laws due to exceptions explained by Noether's theorem and the changing nature of spacetime.
Insights
- Edwin Hubble's discovery in 1929 revealed that galaxies are moving away from us, indicating the universe's expansion, leading to redshift where light wavelengths become longer and cooler in color.
- Noether's theorem explains energy conservation exceptions during cosmological redshift by linking them to symmetries in the universe, challenging the concept of universal truths in physics shown by general relativity and gravitational waves.
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Recent questions
What did Edwin Hubble discover in 1929?
Galaxies moving away, universe expansion.
How does the expansion of the universe affect light?
Light wavelengths stretch out, causing redshift.
What is cosmological redshift and how is it different from Doppler redshift?
Longer wavelengths, less energy, Noether's theorem.
How does Noether's theorem explain energy conservation during cosmological redshift?
Ties energy conservation to universe symmetries.
What challenges the idea of energy conservation during cosmological redshift?
General relativity, gravitational waves, spacetime changes.
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Summary
00:00
Universe's Expansion: Redshift Challenges Energy Conservation
- In 1929, astronomer Edwin Hubble discovered that most galaxies in the universe are moving away from us, indicating the universe's expansion.
- The expansion of the universe causes light to get stretched out, leading to redshift, where light wavelengths become longer and cooler in color.
- Cosmological redshift, different from Doppler redshift, results in longer light wavelengths having less energy, contrary to the law of conservation of energy.
- Energy conservation exceptions during cosmological redshift are explained by Noether's theorem, which ties energy conservation to symmetries in the universe.
- The changing nature of spacetime, as shown by general relativity and gravitational waves, challenges the idea of energy conservation during cosmological redshift, highlighting the limitations of universal truths in physics.
