Description
Convert a supplied Hubble parameter into inverse time.
Cosmology uses several distance measures and often expresses the expansion rate in mixed astronomical units. Scale-factor relations, inverse-Hubble scales and relativistic velocity composition answer different questions; units and the distinction between local algebra and an integrated expansion history are essential.
Convert a supplied Hubble parameter into inverse time.
When to use this tool
Use Hubble Time Gigayear Supplied Unit Factor when checking one explicit cosmological distance, redshift-factor or unit convention.
How to use the tool and how it works
- Enter hubble, inverseSecondsPerInputUnit, secondsPerGigayear. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read hubbleTimeSeconds, hubbleTimeGigayears. Use the output convention below.
Convert a supplied Hubble parameter into inverse time. Require positive hubble, inverseSecondsPerInputUnit and secondsPerGigayear; Hubble time seconds = 1/(hubble*unitFactor), then divide by seconds per gigayear.1
Cosmological distance, volume and lookback-time relations require the appropriate expansion-rate and distance conventions; local factors do not replace integration.2
| Input field | Meaning and units | Accepted input |
|---|---|---|
| hubble | Hubble | Required. Finite number; strictly above 0. |
| inverseSecondsPerInputUnit | Positive factor converting one numeric Hubble input unit to s^-1. | Required. Finite number; strictly above 0. |
| secondsPerGigayear | Seconds Per Gigayear | Required. Finite number; strictly above 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| hubbleTimeSeconds | Hubble Time Seconds | Required. Finite number. |
| hubbleTimeGigayears | Inverse H in gigayears; not the actual age of an arbitrary universe. | Required. Finite number. |
{
"input": {
"hubble": 70,
"inverseSecondsPerInputUnit": 3.240779289444365e-20,
"secondsPerGigayear": 31557600000000000
},
"output": {
"hubbleTimeSeconds": 440811083070195400,
"hubbleTimeGigayears": 13.968460309725561
}
}Limitations and assumptions
- The input conversion factor must turn H into s^-1; inverse H is not the actual age of an arbitrary cosmological model.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use a complete cosmological distance/time calculation and the appropriate observation model when an actual source distance, age or velocity is required.
References
Similar or alternative tools
- Hubble Distance Hunit Factor
Return Hubble distance under a supplied unit conversion.
- Cosmological Lookback Time Local Increment
Return a local lookback-time increment.