top active problems
physics - 2017-03-19T17:26:44Z agoCosmic inflation defined
Is the theory of cosmic inflation correct, and, if so, what are the details of this epoch? What is the hypothetical inflaton field giving rise to inflation? If inflation happened at one point, is it self-sustaining through inflation of quantum-mechanical fluctuations, and thus ongoing in some... Read more
physics - 2017-03-19T17:26:44Z agoFine-tuned Universe defined
The values of the fundamental physical constants are in a narrow range necessary to support carbon-based life. Is this because there exist other universes with different constants, or are our universe’s constants the result of chance, or some other factor or process?
physics - 2017-03-19T17:26:44Z agoDimensionless physical constant defined
At the present time, the values of the dimensionless physical constants cannot be calculated; they are determined only by physical measurement. What is the minimum number of dimensionless physical constants from which all other dimensionless physical constants can be derived? Are... Read more
physics - 2017-03-19T17:26:44Z agoPhysical information defined
Are there physical phenomena, such as wave function collapse or black holes, which irrevocably destroy information about their prior states? How is quantum information stored as a state of a quantum system?
physics - 2017-03-19T17:26:44Z agoYang–Mills theory defined
Given an arbitrary compact gauge group, does a non-trivial quantum Yang–Mills theory with a finite mass gap exist? This problem is also listed as one of the Millennium Prize Problems in mathematics.
physics - 2017-03-19T17:26:44Z agoGrand Unification Theory ("Theory of everything") defined
Is there a theory which explains the values of all fundamental physical constants? Is the theory string theory? Is there a theory which explains why the gauge groups of the standard model are as they are, why observed spacetime has 3 spatial dimensions and 1 temporal dimension, and why all... Read more
physics - 2017-03-19T17:26:44Z agoInterpretation of quantum mechanics defined
How does the quantum description of reality, which includes elements such as the superposition of states and wavefunction collapse or quantum decoherence, give rise to the reality we perceive? Another way of stating this question regards the measurement problem: What constitutes a "measurement"... Read more
physics - 2017-03-19T17:26:43Z agoEntropy (arrow of time) defined
Why did the universe have such low entropy in the past, resulting in the distinction between past and future and the second law of thermodynamics? Why are CP violations observed in certain weak force decays, but not elsewhere? Are CP violations somehow a product of the Second Law of... Read more
biology - 2017-03-19T17:26:43Z agoCell size defined
How do cells determine what size to grow to before dividing?
biology - 2017-03-19T17:26:43Z agoCambrian explosion defined
What is the cause of the apparent rapid diversification of multicellular animal life around the beginning of the Cambrian, resulting in the emergence of almost all modern animal phyla?
biology - 2017-03-19T17:26:43Z agoBlue whale defined
There is not much data on the sexuality of the biggest animal ever.
biology - 2017-03-19T17:26:43Z agoBiological aging divided 5 subproblems
There are a number of hypotheses why senescence occurs including those that it is programmed by gene expression changes and that it is the accumulative damage of biological processes.
biology - 2017-03-19T17:26:43Z agoBasking shark defined
Only the right ovary in this fish appears to function, the reason is unknown.
biology - 2017-03-19T17:26:43Z agoArthropod head problem defined
A long-standing zoological dispute concerning the segmental composition of the heads of the various arthropod groups, and how they are evolutionarily related to each other.
biology - 2017-03-19T17:26:43Z agoAlkaloids defined
The function of these substances in living organisms which produce them is not known. Compared with most other classes of natural compounds, alkaloids are characterized by a great structural diversity and there is no uniform classification of alkaloids. First classification methods have... Read more