Description
Return Hubble distance under a supplied unit conversion.
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.
Return Hubble distance under a supplied unit conversion.
When to use this tool
Use Hubble Distance Hunit Factor when checking one explicit cosmological distance, redshift-factor or unit convention.
How to use the tool and how it works
- Enter hubbleParameter, speed, suppliedHubbleToInverseTime. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read inverseTimeHubble, hubbleDistance. Use the output convention below.
Return Hubble distance under a supplied unit conversion. Require positive Hubble parameter and inverse-time factor and speed >= 0; inverseTimeHubble = H*factor, distance = speed/inverseTimeHubble.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| hubbleParameter | Hubble Parameter | Required. Finite number; strictly above 0. |
| speed | Speed | Required. Finite number; minimum 0. |
| suppliedHubbleToInverseTime | Factor taking numeric Hubble parameter to inverse matching time units. | Required. Finite number; strictly above 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| inverseTimeHubble | Inverse Time Hubble | Required. Finite number. |
| hubbleDistance | Hubble Distance | Required. Finite number. |
{
"input": {
"hubbleParameter": 70,
"speed": 300000,
"suppliedHubbleToInverseTime": 0.001
},
"output": {
"inverseTimeHubble": 0.07,
"hubbleDistance": 4285714.285714285
}
}Limitations and assumptions
- Speed must match the desired distance/time units; this scale is not an integrated light-travel or comoving distance.
- 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 Time Gigayear Supplied Unit Factor
Convert a supplied Hubble parameter into inverse time.
- Cosmological Lookback Time Local Increment
Return a local lookback-time increment.